Firstly, I'll start by saying that I'm not a mechanic. All information I give is from my own personal experience and from research.
I'm creating this post because I believe the PCV system is an important part of your engine and has the potential to cause irreparable damage if not maintained.
PCV (Positive Crankcase Ventilation) System
A crankcase ventilation system is a way for gases to escape in a controlled manner from the crankcase of an internal combustion engine. A common type of such system is a positive crankcase ventilation (PCV) system, the heart of which is a PCV valve—a variable-restriction valve that can react to changing pressure values and intermittently allow the passage of the gases to their intended destination (which nowadays is the engine's intake stream).
http://en.wikipedia.org/wiki/Crankcase_ ... ion_system
1. Excessive Oil Consumption.
2. Sludge Buildup.
3. Engine Wear.
4. Catalyst for Oval Bore/Precat Failure? Unknown.
Approximately 70% of these 'blowby' gases are unburned fuel (HC) that can dilute and contaminate the engine oil, cause corrosion to critical parts and contribute to sludge build up. At higher engine speeds, blowby gases increase crankcase pressure that can cause oil leakage from sealed engine surfaces
PCV valves are generally considered a maintenance item like spark plugs, and should be inspected and replaced periodically (typically every 50,000 miles). The PCV valve siphons blowby vapors from the crankcase into the intake manifold so the vapors do not escape into the atmosphere. One of the beneficial effects of PCV, besides eliminating blowby emissions, is that it pulls moisture out of the crankcase to extend oil life. Moisture can form acids and sludge which can cause major engine damage. So if the PCV valve or hose plugs up, rapid moisture buildup and oil breakdown can result.
The positive crankcase ventilation or PCV valve is an inexpensive and often overlooked component. It is also one possible cause of expensive oil leaks and sludge buildup in an engine.
The PCV system also helps keep moisture, a major contaminant, out of the oil. When an engine is run, a good deal of heat is generated. As the engine cools, condensation forms. The engine oil absorbs this moisture and attempts to hold it. After a period of time the moisture becomes too much and begins to attack the metal parts of the engine.
Should the engine backfire or if the engine is turbo-charged, the PCV valve can close in the opposite direction if the manifold becomes pressurized. This keeps any positive pressure or fuel vapor from entering the crankcase. Even a very small amount of positive pressure can force oil past gaskets and seals and blow gaskets out of place.
As the PCV valve ages several things can happen. Crud and sludge can cause it to stick in the open position. This might result in a misfire at idle and/or oil consumption. A quality shop can test this using a tool called a manometer.
http://www.agcoauto.com/content/plugins ... icleid=197
1ZZ/2ZZ PCV System Operation
The purpose of the PCV system is to remove harmful gases from the crankcase before damage occurs and combine them with the engine's normal incoming air/fuel charge. Fuel injected Toyota vehicles use two different types of closed PCV systems to prevent the escape of crankcase vapours into the atmosphere :
1. Fixed Orifice PCV System
2. PCV System Using Variable Flow PCV Valve
The 1ZZ and 2ZZ engines use the latter. More information about how it works can be read in the following (which appears to be written by Toyota):
The first symptom for me, that rang alarm bells, was a ticky engine at full operating temperature (engine sounded fine when cold). The reason for this, I believe, was down to the degredation of the engine oil by the gases being trapped inside the engine. The oil no longer had the correct viscosity at higher temperatures.
After checking the oil level, the second thing I found was 700ml of oil loss in 500ish miles! This sounds excessive consumption but I believe I have an underlying problem of a leaking valve stem seal (the smell of oil upon startup suggests the oil is dripping onto the cylinders when car is not being used and being burnt upon startup) but I digress. I believe the increased pressure forced more oil through this seal.
Testing and Maintaining
The following is a simple test that can confirm whether the system is operating correctly:
1. Start engine and allow to reach operating temperature.
2. Allow engine to stabalise at idle.
3. Pinch or block hose between PCV valve and vaccum source.
4. Engine should drop around 50 rpm. If engine does not change, check PCV valve and hoses for blockages.
The following link gives a step-by-step guide on getting to the PCV Valve:
http://www.diymytoyota.com/corolla/2zz- ... pcv-valve/
NOTE: I implore you to check the full system and not just the valve. If the hose is blocked, your valve may as well be just a paperweight. I have also read that many people replace their valves after 30-50k miles. My valve was very black inside due to carbon build up, so I decided to replace mine. (£26 from Toyota UK, $10 in America, welcome to ripoff Britton).
Why did it happen to my car?
My engine has supposedly done 30,000 miles. In my mind, this issue shouldn't have arisen. However, I believe my issue was created by one of the following:
1. Engine was from a cat D. Could the crash have caused this?
2. My engine sat around on a palet for 2-3 months in unknown conditions before being placed into my car.
Now that I have cleaned my valve, my car is no longer using oil (maybe a tiny bit, valve stem seal?). This week, my PCV system is to be checked and cleaned, valve replaced and new oil put in.
Whether I have cured my oil usage problem or not, I believe this post holds valuable information to all. Especially considering checking and maintaining the system is cheap and easy.